Wastewater pretreatment method and sewage treatment method using the pretreament method

Abstract

A pretreatment method is provided, which comprises the following steps: (1) wastewater feed is introduced into a first end of a first aeration basin, and is mixed with a first concentrated mixed liquor to obtain a first mixed liquor; (2) the first mixed liquor is aerated in the aeration stage of the first aeration basin to obtain a second mixed liquor at a second end of the first aeration basin; (3) the second mixed liquor is introduced into a first sedimentation basin to obtain a supernatant and the first concentrated mixed liquor; (4) the supernatant is discharged and at least a part of the first concentrated mixed liquor is returned to the first end of the first aeration basin. At the same time, a sewage treatment method using the wastewater pretreatment method is provided. The pretreatment method can be used steadily for a long time without discharging sludge.

What is claimed is:  
     
       1. A sewage treatment method, comprising the following steps:
 (1) introducing a wastewater feed into a first end of a first aeration basin to mix with a first concentrated mixed liquor to obtain a first mixed liquor; 
 (2) aerating the first mixed liquor in an aeration section of the first aeration basin to obtain a second mixed liquor at a second end of the first aeration basin; 
 (3) introducing the second mixed liquor to a first sedimentation basin to perform a sedimentation treatment to obtain a supernatant liquid and the first concentrated mixed liquor; 
 (4) discharging the supernatant liquid, and returning at least a part of the first concentrated mixed liquor to the first end of the first aeration basin so as to have a sludge age of greater than 50 days, wherein the ratio of the aeration treatment time of the first aeration basin to the sedimentation treatment time of the first sedimentation basin is 1:0.5 to 1:6; and 
 (5) passing the supernatant liquid through a biologic regulation zone, a second aeration zone and a second sedimentation zone in turn to obtain a first water effluent and a second concentrated mixed liquor, and returning a first part of the second concentrated mixed liquor to the biologic regulation zone. 
 
     
     
       2. The sewage treatment method according to  claim 1 , wherein the first mixed liquor has a sludge concentration of 2,000 to 30,000 mg/L. 
     
     
       3. The sewage treatment method according to  claim 1 , the aeration treatment time of the first aeration basin is 0.1 to 4 h. 
     
     
       4. The sewage treatment method according to  claim 1 , wherein the chemical oxygen consumption (COD) of the supernatant liquid is 30 to 500 mg/L. 
     
     
       5. The sewage treatment method according to  claim 1 , wherein an organic nutrition and/or sludge feed is further introduced together with the wastewater feed into the first end of the first aeration basin and mixed with the first concentrated mixed liquor to obtain the first mixed liquor, the organic nutrition is a domestic sewage containing biodegradable organics, an industrial wastewater derived from agricultural products as raw materials, or a suitable carbon source, and the sludge is a sludge containing an activated sludge generated in a sewage biotreatment process. 
     
     
       6. The sewage treatment method according to  claim 1 , the aeration treatment in the step (2) is performed in a manner of intermittent aeration or continuous aeration. 
     
     
       7. The sewage treatment method according to  claim 1  in the step (2), the second mixed liquor has a dissolved oxygen concentration of 0.1 to 4 mg/L. 
     
     
       8. The sewage treatment according to  claim 1 , the first mixed liquor, the second mixed liquor and the first concentrated mixed liquor contain facultative microorganisms as dominant floras. 
     
     
       9. The sewage treatment method according to  claim 1 , wherein the first aeration basin and the first sedimentation basin are operated in plug flow manner. 
     
     
       10. The sewage treatment method according to  claim 1 , the fluid residence time of the biologic regulation zone is 0.2 to 2 h. 
     
     
       11. The sewage treatment method according to  claim 1 , wherein the aeration treatment time of the second aeration zone is 0.5 to 4 h. 
     
     
       12. The sewage treatment method according to  claim 1 , wherein the sedimentation treatment time is 0.8 to 6 h. 
     
     
       13. The sewage treatment method according to  claim 1 , the biologic regulation zone comprises an anaerobic section and an anoxic section, the supernatant liquid and the first part of the second concentrated mixed liquor are mixed in and then pass through the anaerobic section to obtain a third mixed liquor, the third mixed liquor and a first part of a fifth mixed liquor are mixed in and pass through the anoxic section to obtain a fourth mixed liquor, the fourth mixed liquor enters the second aeration zone and is subjected to aeration treatment to obtain the fifth mixed liquor, the first part of the fifth mixed liquor returns to the anoxic section, the residual part of the fifth mixed liquor enters the second sedimentation zone and is separated to obtain the first water effluent and the second concentrated mixed liquor, and the first part of the second concentrated mixed liquor returns to the anaerobic section. 
     
     
       14. The sewage treatment method according to  claim 13 , wherein the anaerobic section of the biologic regulation zone has a fluid residence time of 0.1 to 1.5 h. 
     
     
       15. The sewage treatment method according to  claim 13 , wherein the anoxic section of the biologic regulation zone has a fluid residence time of 0.1 to 1.8 h. 
     
     
       16. The sewage treatment method according to  claim 13  wherein the ratio of the fluid residence time of the anaerobic section to the fluid residence time of the anoxic section in the biologic regulation zone is 1:0.5 to 1:6. 
     
     
       17. The sewage treatment method according to  claim 13 , wherein the fourth mixed liquor has a sludge concentration of 2000 to 6000 mg/L. 
     
     
       18. The sewage treatment method according to  claim 13 , wherein the first part of the fifth mixed liquor has a flow rate of 10% to 150% relative to the flow rate of the sewage feed. 
     
     
       19. The sewage treatment method according to  claim 13 , wherein the first part of the second concentrated mixed liquor has a flow rate of 10% to 150% relative to the flow rate of the sewage feed. 
     
     
       20. The sewage treatment method according to  claim 13 , wherein at least part of the residual part of the second concentrated mixed liquor returns to the first end of the first aeration basin of the wastewater pretreatment method. 
     
     
       21. The sewage treatment method according to  claim 1 , wherein the supernatant liquid is used as a sewage feed and subjected to a biotreatment according to Wuhrmann process, A/O process, Bardenpho process, Phoredox process, A 2 /O process, reversed A 2 /O process, UCT process, MUCT process, VIP process, OWASA process, JHB process, TNCU process, Dephanox process, BCFS process, MSBR process, SBR process, AB process, oxidation ditch process, biomembrane process, moving bed process or a combination thereof, to obtain the first water effluent. 
     
     
       22. The sewage treatment method according to  claim 1 , wherein the first water effluent is introduced to a flocculation and clarification basin for the treatment of flocculation and clarification to obtain a second water effluent and a flocculation sludge. 
     
     
       23. The sewage treatment method according to  claim 22 , wherein at least part, of the flocculation sludge returns to the first end of the first aeration basin of the wastewater pretreatment method.